Optical lenses are used in a variety of optical instruments, such as in telescopes and binoculars, microscopes, endoscopes, and other viewing devices such as technoscopes, periscopes, and the like.
Optical lenses in the aforementioned applications are arranged as a rule in a shaft one after the other, in contact with one another or at a distance from each other, as a lens system. In endoscopes in particular, as well as in other viewing devices, lenses are often installed in the form of bar lenses.
Lenses in such a system are secured in place in the shaft, in that the external lenses of the system are tensed against one another in ring-shaped outer areas of their front surface by a securing device. Several lenses can be locked in place together if the lenses are placed against one another crown-to-crown or if distance holders, touching the lenses on ring-shaped outer areas of their front surfaces, are firmly pressed between pairs of neighboring lenses or between one lens and another component of the optical system such as the securing device. These distance holders are produced from metallic materials, especially brass, monel, China silver, or copper beryllium alloys
Publication DE 197 32 991 8 presents an additional securing method for rod lenses of a lens system in a shaft. Here the lenses are held in their respective desired position by a contracting element positioned radially between the lens and the shaft.
As proposed in publication DE 197 50 685, it is also possible to cement lenses into the lens system shaft after they have been inserted into their desired position and centered.
A method in common use because it is very simple, however, is to secure and position the lenses in the shaft by means of a screwed-in securing device and a distance holder.